1. Field of the Invention
The present invention relates in general to a fluorescent-light image display apparatus for displaying a fluorescent-light image obtained of the fluorescent-light emitted from a fluorescent drugs (extrinsic fluorophores) that has been injected in advance into an examination area of a living tissue subject (hereinafter target subject) upon irradiation thereof by a excitation light, or a fluorescent-light image obtained of the autofluorescent-light emitted from the intrinsic fluorophores of a target subject, into which a fluorescent drugs (extrinsic fluorophores) has not been injected, upon irradiation thereof by a excitation light.
2. Description of the Related Art
There are known in the field of fluorescent-light image diagnostic apparatuses for displaying a fluorescent-light image based on the fluorescent-light emitted from an examination area of a target subject upon irradiation thereof by a excitation light having a wavelength within the wavelength range of the intrinsic fluorophores of aforementioned target subject or a fluorescent-light image based on the fluorescent-light emitted from a fluorescent drugs (extrinsic fluorophores), which has been injected in advance into a target subject under examination, upon irradiation thereof by a excitation light.
For example, technologies have been proposed that make use of the fact that the intensity of the fluorescent-light emitted from a normal tissue differs from the intensity of the fluorescent-light emitted from a diseased tissue when a target subject is irradiated by a excitation light having a wavelength within the wavelength range of the intrinsic fluorophores of the target subject, wherein, by receiving the fluorescent-light emitted from a target subject upon irradiation thereof by a excitation light having a wavelength within the wavelength range of the intrinsic fluorophores of the target subject, the location and range of penetration of a diseased tissue is displayed as a fluorescent-light image.
Normally, when a target subject is irradiated by a excitation light, because a high-intensity fluorescent-light is emitted from a normal tissue, as shown by the solid line in FIG. 8, and a weak-intensity fluorescent-light is emitted from a diseased tissue, as shown by the broken line in FIG. 8, by measuring the intensity of the fluorescent-light emitted from aforementioned target subject, it can be determined whether the target subject is in a normal or a diseased state.
However, for cases in which the intensity of the fluorescent-light emitted from a target subject upon irradiation thereof by a excitation light is displayed as an image, because there is unevenness on the surface of a target subject, the intensity of the excitation light irradiating the target subject is not of a uniform intensity. Further, although the intensity of the fluorescent-light emitted from the target subject is substantially proportional to the intensity of the excitation light, the intensity of aforementioned fluorescent-light becomes weaker in inverse proportion to the square of the distance between the excitation light and the target subject. Therefore, there are cases in which the fluorescent-light received from diseased tissue located at a position closer to the excitation light source than normal tissue is of a higher intensity than the fluorescent-light received from normal tissue located further from said light source, and the state of the tissue of the target subject under examination cannot be accurately recognized based solely on the data relating to the intensity of the fluorescent-light received from the target subject upon irradiation thereof with a excitation light. In order to remedy the problems described above, the applicants of the present application propose a method of displaying a fluorescent-light image obtained based on the factor obtained by dividing the ratio of two types of fluorescent-light intensities obtained of different wavelength ranges. That is to say: an image display method of displaying an image based on the difference in the form of the fluorescence spectra reflecting the tissue-state of a target subject; a method of displaying a fluorescent-light image comprising the steps of: irradiating a target subject with a reference light in the near-infrared spectrum, which shows uniform absorption characteristics for a wide variety of target subjects; detecting the intensity of the reflected light reflected by said target subject; determining the ratio between the intensity of said reflected light and fluorescent light intensity by division; and displaying a fluorescent light image based on the factor of said division, among others.
In addition, fluorescent-light image display methods wherein the hue, which is one of the three color properties, is determined based on the ratio between aforementioned two intensities of fluorescent-light or the ratio between the intensity of the reflected-light of the reference-light and the intensity of the fluorescent-light, and the luminosity, which is one of the three color properties, is determined based on the intensity of the reflected-light of the reference-light and the fluorescent-light image is displayed, etc., are being developed.
Further, the fluorescent-light image display apparatus based on the technology described above comprises a excitation light emitting means for projecting excitation light, an illuminating-light emitting means for projecting illuminating-light, a fluorescent-light image display means for displaying a fluorescent light image obtaining means which images the fluorescent light emitted from an examination area which has been irradiated by a excitation light, a reflectance image obtaining means which images the reflected light reflected by said examination area which has been illuminated by an illuminating light, a fluorescent light image display means which displays a fluorescent light image, and a reflectance image display means which displays a reflectance image, wherein these types of fluorescent-light image obtaining means are in many cases provided in the configuration of an endoscope for insertion into a body cavity of a patient, a colposcope, or a surgical microscope.
According to the conventional fluorescent-light image obtaining apparatuses described above, in order to ensure the safety of a patient, the output of the excitation light is set so that the density of the energy of the excitation light projected onto the area under examination is smaller than an MPE value determined according to the JIS safety standard. On the other hand, the fluorescent-light emitted from an area under examination that has been irradiated by the excitation light is extremely weak, and in order to obtain a fluorescent-light image having a good S/N ratio, because it is desirable that the output of the excitation light be as large as possible, it is often the case that the output of the excitation light is set so that the energy density of the excitation light is a value only slightly smaller than the MPE value.
Because of this, for cases in which there is an irregularity with regard to an increase in the output of the excitation light emitted by the excitation light emitting means of a conventional fluorescent-light image obtaining apparatus, the output of the excitation light exceeds the set value, and there is a fear that the target subject will be irradiated by a excitation light having an energy density larger than the predetermined value.
The present invention has been developed in consideration of the circumstances described above, and it is a primary object of the present invention to provide a fluorescent-light image display apparatus in which there is no projection onto an area under examination of excitation light having an energy level larger than a predetermined value, even for cases in which there is an irregularity regarding an increase in the output of the excitation light, whereby the safety of the apparatus is improved.
The fluorescent-light image display apparatus according to the present invention comprises a excitation light emitting means for emitting excitation light, an illuminating-light emitting means for emitting reference-light, a fluorescent-light image obtaining means for obtaining an image formed by the fluorescent-light emitted from an examination area of a target subject upon the irradiation thereof by the excitation light, a reflectance image obtaining means for obtaining a reflectance image formed by the reflected-light reflected from an examination area of a target subject upon the irradiation thereof by the reference-light, a fluorescent-light image display means for displaying a fluorescent-light image based on a fluorescent-light image, and a reflectance image displaying means for displaying a reflectance image based on the reflectance image, wherein the excitation light emitting means is provided with an irregularity detecting means for detecting irregular increases occurring in the output of the excitation light, and a excitation light emission stopping means for stopping the emission of the excitation light being projected onto a target subject under examination, according to the detection of an irregularity by the irregularity detecting means.
Here, xe2x80x9ca fluorescent-light image based on a fluorescent-light imagexe2x80x9d can refer to: any type of fluorescent-light image formed based on at least one type of fluorescent-light image; and more specifically, to a fluorescent-light image based on the ratio between two types of fluorescent-light images or a fluorescent-light image based on the ratio between a fluorescent-light image and an IR reflected-light image formed of the reflected-light of a near-infrared light; or a fluorescent-light image for which the hue has been determined based upon the ratio between two types of fluorescent-light images and the brightness has been determined based upon an IR reflected-light image.
In addition, the fluorescent-light image display apparatus according to the present invention can further comprise a switching means capable of switching, by use of an input operation, between a fluorescent-light image display and viewing mode, in which the excitation light is projected onto an examination area of a target subject and a fluorescent-light image obtained, and a reflectance image display and viewing mode, in which the illuminating-light is projected onto a target subject under examination and a reflectance image obtained, and a reflectance image viewing mode setting means for switching from the fluorescent-light image viewing mode to the reflectance image viewing mode when an irregularity is detected by the irregularity detecting means while the apparatus is in the fluorescent-light image viewing mode.
Further, the fluorescent-light image display apparatus according to the present invention can be further provided with an irregularity notification means for providing notification that an irregularity has occurred, corresponding to the detection of an irregularity by the irregularity detecting means.
Here, xe2x80x9can irregularity notification means for providing notification that an irregularity has occurredxe2x80x9d can refer to any type of means that provides notification to an operator that an irregularity has occurred; more specifically, a message indicating that an irregularity has occurred can be displayed on the display means, a buzzer or other warning sound can be sounded, etc.
A means that can detect that the excitation light emitted from the excitation light emitting means or the output of emitted light having an output corresponding to the output of the excitation light is greater than a predetermined value can be used as the irregularity detecting means.
Further, if the excitation light emitting means is a means provided with a excitation light source for producing excitation light and a drive means for providing drive-current to said excitation light source, a drive-current detecting means for detecting that the drive current is greater than a predetermined value can be used as the irregularity detecting means.
If the excitation light emitting means is a means provided with a excitation light source for increasing the output of the emission of excitation light if the temperature falls and a temperature regulating means for adjusting the temperature of said excitation light source, a temperature detecting means for detecting that the temperature of the excitation light source is below a predetermined value can be used as the irregularity detecting means.
The irregularity detecting means can be a means provided with at least two detecting means from among the emission-output detecting means, the drive-current detecting means, and the temperature detecting means described above.
If the excitation light emitting means is a means provided with a excitation light source for producing excitation light and a drive means for supplying drive-current to said excitation light source, a drive stopping means for stopping the supply of drive-current to the excitation light source can be used as the excitation light emission stopping means.
Further, an optical path cutoff means for cutting off the optical path between the excitation light emitting means to and an examination area of a target subject, of the excitation light can be used as the excitation light emission stopping means.
As to the wavelength band of the excitation light, a wavelength band in the range of 400-420 nm can be used. Further, a semiconductor laser can be used as the excitation light source; in particular, it is preferable that a GaN semiconductor laser is used.
According to the fluorescent-light image display apparatus of the configuration described above according to the present invention, when an irregular increase in the output of the excitation light occurs, because the emission of excitation light onto the target area is stopped, the patient is not irradiated with excitation light having an energy density above a predetermined value, and the safety of the fluorescent-light image display apparatus is improved.
In addition, for cases in which a fluorescent-light image display apparatus provided as part of an endoscope apparatus, etc. that switches between a fluorescent-light image viewing mode, in which a target subject is irradiated with a excitation light, a fluorescent-light image formed of the fluorescent-light emitted from the target subject upon irradiation thereof by the excitation light is obtained and a fluorescent-light image based on the fluorescent-light image is displayed, and a reflectance image display mode, in which a target subject is illuminated with an illuminating-light, a reflectance image formed of the reflected-light of the illuminating-light reflected from the target subject upon illumination thereof by the illuminating-light is formed, and a reflectance image based on the reflectance image is displayed, and displays a fluorescent-light image or a reflectance image is used: first, in the reflectance image viewing mode, while viewing a reflectance image displayed on the display, etc., an operator inserts the insertion portion of the endoscope apparatus into the portion of the body of the patient near the location of the area under examination; after which, the operator switches to the fluorescent-light image viewing mode and the obtaining and displaying of a fluorescent-light image is performed; and after viewing of said fluorescent-light image has been completed, the operator again switches to the reflectance image viewing mode, and while viewing the displayed reflectance image, removes the insertion portion of the endoscope apparatus from the body of the patient. Therefore, if the emission of the excitation light stops while in the fluorescent-light image viewing mode, interference occurs in the fluorescent-light image appearing on the display, and there are cases for which an operator cannot clearly view the examination area of a target subject.
According to the fluorescent-light image display apparatus of the present invention, a fluorescent-light image viewing mode and a reflectance image viewing mode are switched between and viewing is performed, and by stopping the emission of the excitation light and automatically switching to the reflectance image viewing mode when an irregularity occurs in the excitation light emitting means, a reflectance image is displayed instead of the fluorescent-light image of the examination area of a target subject. Therefore, even if an irregularity occurs in the excitation light emitting means, a patient is not irradiated with excitation light having an energy density above a predetermined value, and furthermore, because an operator can continue to view the examination area of a target subject, the safety level can be improved even for a fluorescent-light image display apparatus in which a fluorescent-light image viewing mode and a reflectance image viewing mode are switched between and viewing is performed.
For cases in which an irregularity occurs in the excitation light emitting means, because notification indicative thereof is provided to the operator, the operator can take appropriate measures, and the safety level of the apparatus is thereby improved a level.
If an emission-output detecting means for detecting that the output of the excitation light is above a setting value is used as the irregularity detecting means, the emission of the excitation light can be stopped when the output thereof is detected to be above a predetermined value.
If a drive-current detecting means for detecting that the drive-current supplied to the excitation light source is above a predetermined value is used as the irregularity detecting means, for cases in which excessive drive-current is supplied to the excitation light source, that is, for cases in which the possibility that the output of the excitation light will increase is great, the emission of the excitation light can be stopped.
If a temperature detecting means for detecting that the temperature of the excitation light source is below a predetermined value is used as the irregularity detecting means, for cases in which an irregularity occurs in the temperature regulating means and the excitation light source has been excessively cooled, that is, when there is a fear that the output of the excitation light will increase, the emission of the excitation light can be stopped.
For cases in which at least two detecting means from among an emission-output detecting means, a drive current detecting means and a temperature detecting means are provided, even if one of the detecting means malfunctions, because an irregularity in the excitation light means can be detected by the other, properly functioning detecting means, the emission of the excitation light can reliably be stopped when an irregularity occurs.
Further, by using excitation light of a wavelength within the 400-420 nm wavelength range, more reliable data of the target subject can be obtained. Also, by using a GaN semiconductor laser as the excitation light source, it is possible to make the apparatus more compact, and to reduce cost.